This invention relates to a new compound, i.e., thiohumic acid, and to a heavy metal adsorbent containing this new compound as its active ingredient.
In recent years, pollution of rivers, lakes and sea water with heavy metal ions contained in industrial effluents has become a serious social problem and, consequently, the elimination of heavy metal ions in industrial effluents has become necessary for preventing environmental pollution. It has hitherto been proposed for removing heavy metal ions in water to precipitate these ions as sulfides, carbonates or hydroxides, adsorb them with active carbon, replace them with an ion exchange resin and complex them with a chelate-forming agent. However, such methods are unsuited for treating a large amount of liquids such as industrial effluents, as these methods require expensive treating agents and the rate of removal they achieve is limited.
It is known that humic acid exhibits high adsorptivity for various heavy metal ions, such as copper and cadmium ions. However, humic acid possesses poor adsorptivity for mercury ions and cannot be used as an adsorbent intended for removing mercury. In the chemical industry field, therefore, there is a great demand for the development of a new adsorbent which can economically be prepared and has a high adsorptivity for various heavy metal ions including mercury ions.